Technical Field
The present invention relates to a gas drainage method, and in particular to a gas drainage
liquid nitrogen cyclic freeze-thaw permeability-improvement and pressure relief method.
Related Art
Gas disaster is a main reason causing the catastrophic disaster of coal mines in China. Along with the high-efficiency intensification and the increased mining depth of the coal mines, the emission rate of gas is higher and higher, and the gas explosion and the gas burst have become a difficulty to be solved of mines. At present, gas drainage is one of most effective ways for solving the gas disaster. The coal bed in China is generally the high-gas low-permeability coal bed, so the gas is difficult to drain. Solving the problems of low gas drainage concentration and small emission amount is always the most important thing for controlling the gas disaster. At present, the permeability of the coal bed is increased by generally adopting the methods such as hydraulic fracturing, hydraulic slotting and presplitting blasting; however, as the mining depth is increased, the permeability of the coal mass is poor and poor; and a conventional coal bed permeability improvement gas drainage method is small in fracturing permeability improvement range, and a large-area gas drainage crack net cannot be formed in the coal mass, so the gas drainage rate is low, and the gas control effect is not ideal.